1. Field of the Invention
The invention relates to a safety cap for connecting a cannula hub to a cannula comprising a sleeve having a tubular wall whose one end contains an axial aperture from which extends an outwardly flared cone-shaped funnel and in whose range radial projections are designed on the inner wall surface which, in case of rotation of the sleeve, cooperate with longitudinal wings at the cannula hub.
2. Description of Related Art
One of the most frequent professional accidents is caused by being stuck by a used cannula with resultant infections. Therefore, the rules for accident prevention provide that, upon the use of the cannula, cannula safety caps which do not have a cone-shaped funnel should not be slipped on again, because the repeated slip-on of such safety caps is particularly risky. As recommended by the rules for prevention of accidents, the used cannula without the safety cap should be thrown directly into a specific cannula bin. Said recommendation is rather doubtful for several reasons: Cannula bins are not always available where injections are made or blood is removed by a physician, and the risk of an accident during the transport of the unprotected cannula to a cannula garbage bin is big; for removing the unprotected cannula from the syringe and for throwing it into a bin, the cannula hub must be often gripped with the resultant risk that the fingers come into contact with matter from the patient; the disposal of a non-protected cannula in an optional container, e.g. a bag, highly endangers the waste disposal staff.
A safety cap of the type mentioned at the outset hereof and disclosed in U.S. Pat. No. 4,610,667 is adapted to reduce the safety risk during the assembling with the used cannula in that, by the cone-shaped funnel, the sharp cannula tip is introduced into the opening of the sleeve so that, due to the reduced target accuracy of the user, stick wounds caused by a used cannula at his hand holding the safety cap are avoided. Further, in case of approximation of the used cannula, the cone-shaped funnel forms a protection against infected fluid dripping from said used cannula. To keep the cannula hub and the safety cap together during the waste disposal, there are provided flexible gripper arms directed radially inwardly which engage the cannula hub like barbs to prevent both elements from being moved apart axially. Said configuration calls for a specific measure to permit the separation of the safety cap from the unused cannula. To this effect, between cone-shaped funnel and cannula hub, there are formed flaps adapted to be broken away and keeping the cannula hub out of reach of the gripper arms. Said flaps need be broken down in order to allow the removal of the safety cap. In connection with a cannula hub assembled with a syringe cone, this is effected by a vigorous rotation of the safety cap. Such a procedure is most circumstantial. It is another disadvantage that, by unintentional exertion of axial force, the safety cap may be shifted against the cannula hub thus causing operativeness of the gripper arms so that the safety cap cannot be removed. After all, the cannula/safety cap assembly becomes useless and has to be replaced. Moreover, when the flaps are broken down, plastic particles may be set free which unfavorably may adhere to the cannula thus endangering the patient. Removal of the used cannula with the reapplied safety cap from the syringe cone is faciliated in that the longitudinal wings of the cannula hub extend between the projections formed between paraxial longitudinal flanges on the inner wall surface of the safety cap. If the latter is turned on the cannula hub, they abut against the longitudinal flanges so that the safety cap is arrested nonrotatingly on the cannula hub to serve as a means for the contactless, contamination-resistant removal of the cannula from the syringe cone.
It is the object of an invention to improve the safety cap mentioned at the outset hereof so that the axial removal of said safety cap from the unused cannula secured to a syringe is facilitated.